1. Field of the Invention
The invention relates to a method for preparing black phosphorus or black phosphorus-carbon composite, lithium rechargeable battery comprising the prepared black phosphorus or black phosphorus-carbon composite and method for using the rechargeable battery.
2. Description of the Related Art
Lithium ion rechargeable batteries have been used as portable power sources for a wide variety of electronic devices such as cellular phones, notebook computers and camcorders. The rechargeable batteries have lithium as its anode material and shows the very excellent performance since lithium itself has such a high energy density of 3860 mAh/g. However, when using the lithium as the anode material of the rechargeable batteries, there occurs a problem of stability reduction of the rechargeable batteries during charge. Further, there occurs a problem of low charge and discharge efficiency.
In order to solve the problems, researches on the lithium alloy has been carried out. The lithium alloy has higher energy density and larger charge and discharge capacity per weight or per volume than those of the carbon-based anode material. However, the lithium alloy still suffer from poor capacity retention since a large volume change occurs during the charge and discharge, which cause the break of the active materials and the decrease of capacity during the cycle of the battery.
Intensive researches on the silicone-based composite also have been carried out. However, such technique using silicone-based composite as the anode material of the rechargeable batteries has a problem that there is no improvement in its charge and discharge characteristics as well as its cycle characteristics even though there is an increase of the capacity during the initial cycles of the batteries.
Meanwhile, phosphorus, which is an element of the fifth group in the periodic table, has a large theoretical capacity of 2595 mAh/g so as that it can be used suitably as the anode materials of the rechargeable batteries. Phosphorus has three main allotropes i.e. white, red and black. Among these several modifications of allotropes, black phosphorus is thermodynamically the most stable, insoluble in most solvents, practically non-flammable, and chemically the least reactive form and exists in three known crystalline modifications (orthorhombic, rhombohedral and simple cubic), as well as in an amorphous form.
Since orthorhombic black phosphorus was obtained from the white one at 200° C. and 1.2 GPa in the prior art, many studies designed to synthesize black phosphorus have been carried out. However, the basic concept of a high temperature and high pressure being required in the synthesis has not been changed, and to this end it still remains difficult and inefficient to synthesize black phosphorus and to apply it commercially.